Mineralogy, thermobarometry and tectonic setting implication of garnet-clinopyroxene amphibolite in the Nain ophiolitic complex


1 گروه زمین شناسی دانشگده علوم پایه دانشگاه بین المللی امام خمینی

2 Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran

3 Department of Geology, Faculty of Sciences, Imam Khomeini International University, Qazvin, Iran


The metabasites of the Nain ophiolites consisting of amphibole + plagioclase ± garnet ± clinopyroxene ± epidote rock forming minerals. On the basis of mineralogical paragenesis, thermobarometry calculations, textural and mineral relations as well as the stability field of different mineralogical assemblages, the metamorphic evolution of the area contain three metamorphic stages as prograde, peak and retrograde indicating clockwise metamorphic trajectory. According to the mineralogical evidences and thermobarometry data, the temperature and the pressure conditions of metamorphic climax stage of garnet-clinopyroxene amphibolite samples is equivalent to high pressure granulite subfacies and transition zone between amphibolite and high pressure granulite. The genesis setting of such high grade metamorphic rocks in the ophiolitic regions are the root of mature islands arc and hot subduction zones. The consensus about the existence of narrow and young oceanic basins (back arc) derived from Neo-Tethys subduction beneath Central Iran micro-continent indicating subduction of young oceanic slab in a hot subduction zone and the generation of high grade metabasites in the Nain ophiolitic complex.